Preheat the oven to 400°F.
In a large skillet, heat a drizzle of oil over medium-high heat and cook the onion for a few minutes, until soft. Add the red pepper and sausage and cook for a few more minutes, then the potatoes, cover and cook for 5-10 minutes, until the potatoes are tender. Remove the lid and add the green onions and garlic. Cook for another minute or two, then spread the mixture into a 9"x13" pan that has been sprayed with nonstick spray.
Meanwhile, stir the eggs and half & half with a fork or whisk, until well blended. Season with salt and pepper and stir in half the cheese. Pour over the vegetables and sprinkle with cheese. Bake for about 20 minutes, until set. Cool completely and then cover and refrigerate for up to 2 days. Serve cold, cut into squares or triangles.